Various devices have been previously designed to measure the sharpness of cutting edges. For example, U.S. Pat. No. 4,178,797 to Kozlowski discloses a machine for testing the sharpness of knives, particularly surgical knives, where the sharpness of a blade is determined by the number of turns required to cut through a cylindrical spinning rod made of rubber or plastic. U.S. Pat. No. 2,472,994 to Vars discloses a device which tests the sharpness of a knife blade by causing a piece of paper to be drawn downwardly toward the blade and measuring the depth of cut in the paper. U.S. Pat. No. 3,827,281 to Hamel discloses a method and apparatus for testing the abrasiveness of materials, such as paper, by pressing an easily dulled cutting edge through a plurality of paper layers to ascertain the abrasion characteristics of the paper.
These available devices and methods for testing knife blade sharpness are deficient in several respects. For example, to obtain sharpness measurements using the apparatus disclosed in U.S. Pat. No. 4,178,797 to Kozlowski, an operator must count the number of turns of the handle until the knife cuts through the cutting medium. Such sharpness measurements can be imprecise and inaccurate, not to mention unreliable and not easily reproduced. In addition, the apparatus can only measure the sharpness of a single, specific portion of the knife.
The apparatus disclosed in U.S. Pat. No. 2,472,994 to Vars exhibits similar deficiencies in terms of accuracy, precision and reproducibility of sharpness measurements. The Vars apparatus can only measure the depth of cut in a piece of paper drawn over an edge and does not permit quantitative sharpness measurements to be obtained for discrete portions of an edge or along the entire length of an edge. Thus, the Vars apparatus does not permit one to quantitatively determine whether a cutting edge is uniformly of a desired sharpness.
Finally, the invention described in U.S. Pat. No. 3,827,281 to Hamel is designed to test the abrasiveness of materials, such as paper, by measuring depth of cut through the paper and is not designed to measure the sharpness of an edge, especially discrete portions thereof.
None of these available devices and methods for testing knife edge sharpness can quantitatively measure the sharpness of an edge with a high degree of precision, reliability or reproducibility. In addition, none of these devices and associated methods quantitatively measure the sharpness of an edge at discrete segments of or along a substantial or length of the edge.
In view of these deficiencies, a need exists to provide an apparatus and method for testing the sharpness of cutting edges that is capable of producing quantitative, accurate, reliable and reproducible sharpness measurements. Because typical cutting motions utilize not only specific portions of an edge, but also various lengths of an edge, it would also be beneficial to provide an apparatus and associated method for measuring the sharpness of an edge, at consecutive, discrete points on an edge, and/or along the entire length of the edge.